The way to handle this situation is simply to never enter SSL_read() if there isn't anything to read on the socket. select() or pselect() are your friends, here, because they'll tell you if there's data to read from the underlying file descriptor.
I hope this helps!
-Kyle H
On Oct 5, 2017 02:58, "mahesh gs" <mahesh116@xxxxxxxxx> wrote:
Hi All,I have query regarding the SSL_read on blocking socket. How to come out of blocking SSL_read when we have to close the connection ?As per the documentation SSL_read will only return if there is any data or an error occurred."If the underlying BIO is blocking, SSL_read() will only return, once the read operation has been finished or an error occurred, except when a renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur"I am trying following methodsmethod 1:1) Thread - 1 blocks in SSL_read2) Thread - 2 receive indication to stop the connection from application. Call SSL_Shutdown() to unblock the SSL_read in thread - 1. But this is dangerous as calling SSL_shutdown and SSL_read from different threads on same context can lead to undefined behaviour.method 2:1) Thread - 1 blocks in SSL_read2) Thread - 2 receive indication to stop the connection from application. shutdown the underlying TCP socket using system command (shutdown (socket_id, SHUT_WR)) that cause the SSL_read to unblock.3) Thread - 1 unwind and close the TCP socket (using close(socket_id)). thread -1 cannot call SSL_Shutdown since the TCP socket is shutdown by thread - 2 for write operation. As per my understanding this violates the TLS standard because of not sending out the close notify handshake.How to ensure to come out of blocking SSL_read and initiate SSL_shutdown from same thread?Thanks,Mahesh G S
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